Search Warslik's Woods for 8 Redscale Pitcher Leaves.
Note: This is a small dark bluish-black plant that is not trackable. They are abundant in the Warslik's Woods area between Nye'Caelona, Slaver's Point, and Warslik's Woods poi's on the map. I didn't find any at all near Chalp or Twark areas of Warslik's Woods.
Return to Savix'Host and make him take the medicine.
Take him to Crusader's Cave.
Note: You can fly directly to Crusader Tarrac at the inner gate of the cave to escort him there. [update: 161218] only in proximity to Crusader Tarrac will one receive quest update. Running around the cave itself does not.
(x)Update happened around roughly (639, 247, 1224),(x) you'll have to land for the update to happen